1. What is the general form of the number 85?
- A10*8 + 5
- B10*5 + 8
- C8 + 5
- D100*8 + 5
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Answer: A) 10*8 + 5
The number 85 can be expressed as 10*8 + 5, where 8 is the tens digit and 5 is the units digit.
Class 8 Playing with Numbers — practice questions with answers
Number System · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
2. Which of the following is divisible by 10?
- A470
- B475
- C402
- D455
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Answer: A) 470
A number is divisible by 10 only if its units digit is 0. Among the options, only 470 ends in 0.
3. In the puzzle 2 A + 1 5 = 4 1 (a two-digit addition), what single digit does A stand for?
- A6
- B5
- C7
- D12
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Answer: A) 6
The number 2A plus 15 equals 41, so 2A = 41 - 15 = 26. Thus the units digit A is 6.
4. A number is divisible by 3 if and only if which of the following is true?
- AThe sum of its digits is divisible by 3
- BIts last digit is divisible by 3
- CIts first digit is divisible by 3
- DIts last two digits are divisible by 3
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Answer: A) The sum of its digits is divisible by 3
The divisibility rule for 3 depends on the sum of all the digits being divisible by 3, not on any single digit.
5. How many full boxes of 12 can be packed from 200 apples, and how many apples are left over? Give the number left over.
- A7
- B9
- C8
- D16
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Answer: C) 8
200 divided by 12 gives 16 full boxes (16 * 12 = 192) with a remainder of 200 - 192 = 8 apples left over.
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